The invention relates to a control device of a circuit breaker opening or closing electromagnet, said device comprising at least one coil connected in series with an electronic switch to the terminals of a supply voltage, means for measuring a first voltage, representative of the supply voltage, and means for control of the electromagnet, comprising means for comparison, connected to the means for measuring the first voltage and to a control electrode of the electronic switch, to compare the first voltage with inrush and drop-out thresholds.
Circuit breakers generally comprise a certain number of electrical auxiliaries, more particularly closing electromagnets (XF) or opening electromagnets, notably shunt releases (MX) or under-voltage releases (MN). The electromagnets used in under-voltage releases (MN) have different operating characteristics from those used in shunt releases (MX) or in closing electromagnets (XF). The control devices which are associated thereto are consequently different.
The object of the invention is to achieve a standard control device able to be used indifferently with the three above-mentioned types of auxiliaries and guaranteeing a satisfactory operating safety in all cases.
According to the invention this object is achieved by the fact that the means for comparison compare the first voltage with distinct first and second inrush thresholds and with a drop-out threshold, so as to monitor the flow of an inrush current in the coil during an inrush phase of preset duration when the first voltage reaches one of the inrush thresholds.
According to a development of the invention, at the end of an inrush phase the control means control, during a holding phase, the flow in the coil of a holding current weaker than the inrush current, the device comprising means for measuring the current flowing in the coil, the control means comprising means for regulating the holding current, with means for comparing the current with a preset setpoint value, and means for commanding switching to a new inrush phase when, during a holding phase, the current is less than or equal to a preset fraction of the setpoint value during a second preset duration.
According to another development of the invention, the means for measuring the first voltage comprise numerical means for determining the rms voltage, comprising sampling means and a finite impulse response filter having an equation of the form:
U2=a1A1+a2A2+ - - - +ajAj+ - - - +anAn
      with    ⁢          xe2x80x83        ⁢    Aj    =            ∑      0              m        -        1              ⁢          xe2x80x83        ⁢          U2      i      2      
where U2i is a sample of the first voltage, nxe2x89xa72, mxe2x89xa71, the weighting coefficients aj not all being identical.